This invention relates to an endoscope having an extension guide for observation.
In an endoscope of this type an extension guide is a stub shaft-like section fixed slantwise, for example, at the side wall of a control section housing where an operator operates the endoscope, and an eyepiece section for observation is fitted to the free end portion of the guide. Such a construction is often found in an endoscope of such a type that the base end of a channel tube having a channel for inserting a body cavity treating instrument such as a catheter therein extends through that end wall of the housing which is provided on the side opposite to that in which a sheath to be introduced into the body cavity of a human being is connected. This is because no space enough to fix an eyepiece section is often left at that end of the housing from the standpoint of design consideration. A prism is disposed between the eyepiece section on the extension guide and the base end of an optical fiber bundle which extends from the sheath into the housing. The base end of the optical fiber bundle is optically connected the eyepiece by bending an optical axis through the utilization of the prism. In such a structure a higher degree of skill is required in the adjustment of an observation optical system and, by doing so, the misalignment problem is liable to occur. Further, as the extension guide is limited in its length the operator requires some effects during the observation through the eyepiece section. This is partly due to the fact that as the extension guide is rigid the angle and position of the eyepiece section are restricted. Thus, a cumbersome manual operation is required at the control section housing so that ROI (region of interest) within the body cavity can be observed. Since the eyepiece section is so restricted, such inconvenience is added.
The above-mentioned problem is involved in the endoscope having an eyepiece section not only at the side of the housing, but also at the end of the housing.